Fluid pressure mechanism



oct. 2, 1945. E FOWLER' 2,385,046

FLUID PIRESSURE MEGHANISM Filed Aug. 4, 1943 2 Sheets-Sheet 1 Oct. 2, 1945. FOWLER v 2,386,046

FLUID PRESSURE MECHANISM Filed Aug. 4, 1945 2 Sheets-Sheet 2 Res.

Law Fasunn Res.

Elbverf l'wlez'.

"V I@ @@QM/w Patented Oct. 2, 1945 FLUID PRESSURE MECHANISM Elbert Fowler, Mountvernon, N. Y., assigner to Bendix-Westinghouse Automotive Air Brake Company, Elyria, Ohio, a corporation of Dela- Ware Application August 4, 1943, Serial No. '497,387- 419 claimsl (ci. 23o-2)- This invention relates to iiuid pressure control systems and more particularly to mechanism for producing fluid pressure under substantially high pressures and for controlling the maintenance of these pressures.

The present invention contemplates a mode of operation wherein the intake side of the uid compressor is normally maintained at a pressure well above atmospheric pressure, this mode of operation permitting the compressing of uids to a .relatively high pressure at the output side of the compressor without resulting in correspondingly increased compression ratios, such as4 would occur in the event such a high pressure were obtained from a single stage compressor inthe ordinary manner. In addition to the foregoing, the present invention contemplates a system wherein, after the system has been initially charged with a uid pressure, the system automatically becomes a' closed system, no further fluid being drawn into the compressor from an outside source except such fluid as is necessary to compensate for leakage from various parts of the' system, systems of this nature being particularly applicable to the compression of uid under.conditions such that moistureA present in the uid normally has a very detrimental effect on the operation of the system, aneffect which is largely minimized by the present invention.

It has previously been proposed to provide socalled closed systems for the compression of ,air or other gas in order to prevent the accumulation of excessive moisture in the system such as might be drawn in from the atmosphere, but diiliculty has ybeen experienced in systems of `this type in properly controlling the pressures in the low andhigh pressure portions of the system, and it is accordingly an object of the present invention to provide means for controlling the pressures in the system without unnecessary attention on the part of the operator.

Another object of the invention is to provide in a fluid compressing system `of the above type, means for .maintaining the intake side ofthe compressorat a pressure above that of the surrounding atmosphere.

'Yet another object of the invention is to provide means for controlling the relative pressures in the high and low pressure portions of the system and for maintaining them at 'substan- '.tially predetermined values.

supercharging the compressor at a pressure considerably above that of the surrounding atmos- Dhere.

Another object of the invention is to provide control mechanism for a compressor so constituted as to permit the supplying of high pressure air to one receiver and low pressure air to another receiver by means of a single stage compressor.

A further object of the invention is to provide, in a system of the above type, means for preventing further compression of fluid by the compressor when the desired predetermined pressures are established in the high and low pressure portions of the system. i A still further object of the invention is to pro- A vide a system of -the above type so constituted as to permit the controlled pumping of relatively high pressures with a single stage compressor without the necessity for utilizing correspondingly high compression ratios.

These and other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when considered in connection with the accompanying drawings illustrating two embodiments of the' invention. i

It is to be expressly understood, however, that the drawings are employed for purposes of illustration only and are not designed as a denition of the limits of the invention, reference for the latter being had to the appended claims.

In the drawings, ,wherein similar reference characters denote corresponding elements throughout the several views:

Fig. 1 is a diagrammatic illustration, partially in section, ofa uid compressing system embodying the principles of the present invention, and

Fig. 2 is a diagrammatic illustration, partially in section of another embodiment of the invention.

Referring more particularly to Fig. 1 of the drawings, a uid compressing system embodying the present invention is illustrated therein as including a high pressure reservoir 6 and a low pressure reservoir l, together with a compressor 8, which may be of the well-known rotary type, and which is adapted to supply fluid pressure to the high and low pressure reservoirs as will be more fully explained hereinafter. The compressor 8 includes a casing 9 having a bore I0 anda, rotor ll adapted tobe driven in a4 counter-clockwise direction by a suitable prime' mover, not shown, the rotor being provided with sliding blades l2 in contact withthe wall of .the bore I0, which is of the so-called generated type, and since this compressor is of well-known construction, it will be understood that on oper-l ation of the rotor, fluid will be transferred from an intake port I3 provided in the casing of the compressor to a discharge port I4, the fluid at the same time being compressed to a degree dcpendent on the design of the compressor mechanism. The inlet port I3 is provided with a connection to atmosphere which includes a passage l5 and an atmospheric port I6, communication between the inlet port and the passage I5 being normally prevented by means of a check valve I1 normally maintained in engagement with a valve seat I8 formed at the lower end of the passage I5, through the medium of a spring I9 interposed between the compressor casing and -tween the upper face of the valve and a portion of the casing serving to permit passage of fluid from the compressor to the high pressure reservoir and to prevent the passage of liuid in the other direction from the reservoir to. the discharge port of the compressor. A second outlet chamber 25 is provided as shown, this chamber being provided at its upper end with a port 26 and at its lower end with a port 21,V the port 21 being connected with the discharge port I4 through the medium of a passage 28 formed in the casng. In order that iiuid pressure may be supplied from the compressor to the-low pressure reservoir 1, the second outlet chamber 25 -is connected thereto through the medium of conduit 29, port 26 at the upper end of the outlet chamber 25 being connected with the inlet port I3 of the compressor through` the medium 'of apassage 43l) and a passage 3l i formed in the casing and connected thereto. In order that the connections between the inlet andl outlet ports of the compressor and between these ports and the high and low pressure reservoirs may be properly controlled, the outlet chamber 25 is provided with a valve 32 provided wth an upwardly extending stem 33 slidably mounted in a bore 34 formed in the upper portion of the housing, the valve being normally maintained in the position shown to close the port 21 by means of a spring 35 interposed between the upper end of the casing and a ange 36 formed on the stem of the valve, the tension of the spring 35 being suicient to maintain the valve 32 in a-position to close the port 21 regardless of the degree of pressure existing in the passage 28 connected with the discharge port I4. With the parts in the position shown, it will be understood that operation of the compressor will serve to draw uid into the intake port I3 through atmospheric port I6, passage I5 and check valve I1, and vto` compress this fluid in discharge port I4, whereupon the fluid forces its way past the check valve 22 and thence through the outlet chambers 29 to the high pressure reservoir 5 through the medium of the conduit 2|. l

Assuming that it is desired to limit the pressure in the high pressure reservoir to 600 pounds, for example, means are provided under the control of the pressure in the high pressure reservoir for changing the position ofthe valve'32 when this predetermined pressure is reached,

V:attarde l such means including a pressure-responsive governor 31 of well-known design, a relay valve mechanism 38 and a. iluid pressure actuator mechanism 39 adapted to be controlled by the operation of the governor 31. As will be well understood by those skilled in ,the art, the governor mechanism 31 is provided with a conduit 48 connected with the reservoir 5 and an outlet conduit 4I, together with an`atmospheric port.

not shown, the governor serving normally to establish a connection between the conduit 4I and l the atmospheric port and to prevent communication between the supply conduit 48 and theoutlet conduit 4|. The governor may be adjusted to operate over a predetermined pressure range, and in the event a, maximum pressure of 600 pounds is desired in the high pressure reservoir, the governor may be set in such a manner that when this pressure is reached, the governor will operate to disconnect the conduit 4I from the exhaust port of the governor and to establish a connection between conduits v4l) and 4I, thus supplying fluidpressure to the conduit 4I through the governor at the pressure attaining In the reservoir 6. On a reduction of pressure in the reservoir 6 to 590 pounds, for example, the governor again becomes operative to disestablish the connection between conduits -4I! ancl 4I and to establish a connection between conduit 4I and the atmospheric port, thus permittng iiuid in the conduit 4I to exhaust to atmosphere.

The mechanism 39 is for the purpose of controlling the operation of the valve 32, the mechanism comprising a fluid motor 42 having an inlet chamber 43 and a piston 44 slidably mounted therein and provided with a piston rod 45, together with a secondflu'id motor 46 provided with an inlet chamber 41, a piston 48 and a piston rod 49 connected thereto. In order that the iiuid motors may serve to control the operation of the valve 32, a beam 50 is pivotally connected to the upper ends Yof both the piston rod 45 and the piston rod l49 by'means of pivot pins 5I and 52 respectively, the upper end of the valve stem 33 being pivotally connected to the beam by the means of a pin 53 at a point intermediate the pins 5I and 52. Thus the spring 35 acting on the valve stem 33 in conjunction with pivot 53. beam 59, and pivot pins 5I and 52 serve to nor- -mally maintain the pistons 44 and 48 in the position shown with respect to the inlet chambers 43 and 41, the upward travel of the piston rod 45 being limited by means of a stop 54, and the upward travel of the piston rod 49 being limited by means of a stop 55, the spacing between the upper end of the rod 49 and the stop 55 being such that on upward movement of the piston 48 and rod 49 only, the beam 50 will pivot about the pin 5I on the piston rod 45, and the valve stem 33 will move upward suiliciently to move the valve 32 through only half the distance between the upper end of the port 21 and the lower end of the port 25, downward movement of the rod 45 and the piston 44 being prevented by the abutment of the lower face of the piston against the lower end of the chamber 43. The spacing beonly thus serving to move the valve to the halfway position. and concurrent or sequential movement ar both piston rods serving to move the valve to its extreme upward position through the connections described.

The relay valve mechanism 38 is for the pur- 1- of a port 59 formed in apartition 60 which serves tive to supply. uid pressure to either of the reservoirs, this mechanism including a second l v governor 68, which may be of similar construcconduit 10 and the atmospheric portof the govto separateV the chambers, while the outlet chamber y56 is adapted to be connected with atmosphere through the medium of a port 6I formed in the wall of the outlet chamber. In order that the connection between the inlet and outlet chambers and between the outlet chamber and Aatmosphere may be properly controlled, avalve stem 62 is` slidably mounted in the casing of the relay valve, the stem being provided at its upper end with a valve member 63, and at its lower .end with a piston 64 mounted in a cylinder 65 formed in thelower portion of the casing. a.

spring 66 interposed between ythe lower end of the cylinder 65 and the. lower face oi' the piston serving normally to maintain the piston, rod and valve in upward position wherein the port 59 is open to permit communication between the inlet chamber 58 and' the outlet chamber 56 and the atmospheric port 6I is closed by the upper end of the valve 63. Thus with the parts in the position shown, operation of the governor 31 to establish a connection between conduits 40 and 4I will serve to supply fluid pressure to the chamber 43 ofthe motor 42 through the chamber 58 of the relay valve, port 59, outlet chamber 56 and conduit 51, the uid pressure thus supplied to the 'motor 42 serving to move the piston 44 and the rod 45 upward against the stop 54 to move the valve 32 to mid-position. The chamber 41 of the fluid motor 46 is likewise connected with the conduit 4I through the ymedium of a conduit 61, and thus operation of the governor 31 to supply uid pressure to the motor 42 will likewise supplyuid pressure to the motor 46, causing the piston 46 and the rod 49 to move upward at substantially the same time as the piston 44 and the rod 45 of the motor 42, with the result that the valve 32 will be moved upward to close the lower end of the port 26, thus establishing communication between the outlet chamber and the discharge port I4 of the compressor through the passage 26 and serving to prevent communication between the outlet chamber and the inlet port of the compressor through the passage 30 and the passage 3l. Thus when the pressure in the high pressure reservoir reaches a pressure of 600 pounds, for example, the valve 32 will Ibe moved to its extreme upward position in the manner just described, whereupon, the uid pumped by the compressor will be supplied to the low pressure reservoir 1 through the passage 26, port 21, outlet' chamber 25 and conduit 29.

With the above pressure prevailing in the high pressure reservoir 6, it may b e desirable to maintain a maximum pressure of approximately 100 pounds in the low pressure reservoir 1 in order thatl the compressor may operate on a relatively small compression ratio, and in this case means I is provided for controlling the operation of the relay valve 38 to render the compressor ineffection to the governor 31, the governor being supplied with iiuid pressure from the reservoir 1 through the medium-of conduit 63 and serving to 'supply fluid pressure to a portion of the relay valve 38 through a conduit 16, it being understood that when a pressure of pounds is reached in the reservoir 1, the governor 64 will become 'operative to dis-establish a connection between the ernor, not shown, and toestablish a connection between the supply conduit 69 and the conduit 10, thus supplying pressure from the reservoir 1 Ato the conduit 10. The relay valve mechanism 38 is provided with a chamber 1I above the piston 64, and on operation of the governor to supply uid pressugreto the conduit 10, fluid pressure is also supplied to the chamber 1 I, connected thereto, resulting in downward movement of the piston against the spring 66, and consequent downward movement of the valve 63 to open the port 6I and Aclose the port 59. When this action occurs, fluid pressure will be exhausted from the chamber 43 of the motor 42 through conduit 51, chamber 56 of the relay valve 38 and exhaust port 6I, whereupon the spring 35 will force the valve stem 33 and the beam .50 downward until thepiston 44 abuts the lower end of the iiuid motor 42, whereupon the valve 32 will be in mid-position between ports 26 and 21 and the discharge port I4 will be in communication with the inlet port I3 of the compressor through the passage 28, port 21, outlet chamber 25, port 26, passage 36 and passage 3I, the compressor under this condition of .operation serving merely to recirculate the fluid from the inlet side of the pump to the exhaust side of the pump and back again to the inlet side of the pump, without, however, supplying iluid to either of the reservoirs. Since the outlet chamber 25 is in constant communication with the low pressure reservoir 1 through the medium of conduit 29, the inlet side of the pump under this condition of operation will be at the same pressure as that obtaining 'in the4 low pressure reservoir, the escape of pressure from the inlet port to atmosphere being prevented bymeans of the check valve I1 as heretofore described.

A uid pressure actuator system is also indicated which comprises a iiuid motor 12 having a piston 13 slidably mounted therein and normally maintained at the left end of the motor by means of a spring 14. rI'he piston is provided with a piston rod 15 connected thereto, and serving to actuate a lever 16, which in turn can control the operation of any desired device requiring power actuation for its control. The ilow of iiuid pressure to the motor 12 is controlled through the medium of a self-lapping control valve mechanism 11, which may preferably be constructed in accordance with the principles set forth in the patent to Wilfred A. Eaton, No. 2,204,530, dated f Abe broken off and communication will be established between the Inlet conduiiI 19 and the outlet conduit 80 to supply fluid pressure to the motor 12 in a degree dependent on the degree of displacement of the control pedal. Since the exhaust conduit BI is connected at all times, as shown, to the low pressure reservoir 1, it will be apparent that with the valve in release position, the pressure in this conduit as well as the pressure in the outlet conduit 80 will be the same as that prevailing in the low pressure reservoir, and since this pressure is greater than atmospheric pressure, it is understood that the spring 14 is so tensicned as to insure the return of the piston 13 to the position shown against this pressure, this arrangement thus insuring complete release operation of the fluid motor 12 on release movement of the control pedal 18.

In the operation of this fluid pressure supply system, the parts are initially inthe 'position shown when there is no pressure in either of the reservoirs, and on operation of the compressor, fluid at atmospheric pressure will be drawn into the inlet port4 through the atmospheric port I6, passage I and check valve I1 and after compression in the compressor, will be discharged to the `high pressure reservoir through the discharge port I4, the check valve 22, the outlet chamber 20 and the conduit 2|, this action continuing until such time as the pressure in the high pressure reservoir increases to a point where the governor 31 becomes operative to establish a connection between the conduit 40 and the conduit 4I, whereupon fluid pressure is supplied to the iluid motor 42. through the medium of conduit 4I, chamber 56, port 58, chamber'56, and conduit 51, and to the fluid motor 46 through conduits 4I and 61, the motors 42 and 46 thus becoming effective to move the beam 50 upward and to therefore move the valve 32 upward at the same time to a point where it closes 0E the port 26. When this occurs, the outlet chamber 25 will be placed in communication with the discharge port I4 through thel passage 28 and the' compressox: will b e conditioned to supply-fluid pressure to the lowpressure reservoir 1 through the conduit 29, the uid again being drawn into the compressor through the atmospheric port I6 and past the check valve I1. When the fluid in the low pressure reservoir reaches the desired pres.- sure, the governor 68 becomes operative to establish a connection between conduits 69 and 10, thus supplying fluid pressure to the upper end of the piston 64 in chamber 1I, forcing the piston downward and causing the valvev68 to close the port 59 and open the port 6I to exhaust fluid pressure from the chamber 43 of the iluid motor 42 through conduit51, chamber 56 and port 6I, whereupon the spring 35 moves the valve 32 downward to mid-position, further movement of the valve to close the port 21 Ibeing prevented by the abutment of the piston 44 against the lower end of the fluid motor 42. Thus-both the high and lowpressure reservoirs are supplied with iuid compressed to the desired pressures and until leakage occurs from the system or fluid is used for the operation of the fluid motor 12, the discharge port I4 will be connected with the inlet port I 3 through the passages already described and no further iiuid will be pumped into either of the reservoirs.

If the control valve 11 is now operated to sup-v ply uid pressure to the motor 12, it will be understood that after a number of such opera'- tions, the pressure in the high pressure reservoir. 6 will be decreased to a point wherethe governor 31 will become effective to break off communication between conduits 40 and 4I and establish communication between the conduit 4I and atmosphere, whereupon fluid pressure will be exhausted from chamber 41 of the motor 46 through conduits 6I and 4I permitting the spring 35 to move the valve 32 further downward to close the port 21, and since with the valve in this position, the outlet chamber 25 is connected with the inlet port I3 of the compressor as previously de-` scribed, fluid pressure will 'be supplied to the inlet port from the low pressure reservoir I through conduit 29, outlet chamber 25, port 26, passage 36 and passage 3| to supercharge the compressor and to permit the compressor to pump fluid into the high pressure reservoir 6 through the discharge port I4, check valve 22, outlet chamber 20 and conduit 2|, the supercharging of the inlet side of the compressormesulting in compressor operation at a comparatively low compression ratio to establish a relatively high pressure in the high pressure reservoir. This operation will of course deplete the fluid in the low pressure reservoil` 1, and in the event the governor is set to operate on a 10 l'b. range for example, it will be understood that vwhen the pressure in the low pressure reservoir drops to lbs., .the governor 68 Awill become effective to disestablish the connection between conduits 69 and 16 andto establish a connection between the conduit 16 and atmosphere to exhaust fluid pressure from the chamber II and permit the spring 66 to force the piston and the valve 63 upward again to a point where the valve closes the exhaust port 6I of the relay valve 38. When this action occurs, all the various parts will again be in the position shown on the drawing, and fluid from the low pressure reservoir will be compressed and pumped into the high `pressure reservoir until such time as the governor 31 again` acts to establish communication between conduits 46 and 4I, at which time the valve 32 will be moved upward to open the port 21 and close the port 26, thus permitting the compressor to draw in iiuid from the atmospheric port and compress it into the low pressure reservoir to replace that which has #been pumped into the high pressure reservoir during the supercharging operation, and it will be understood that on con'- tinued operation of the mechanism, a condition of balance will be reached wherein there is a sulcient supply of fluid pressure in 'both the reservoirs and in the system to take care of al1 ordinary requirements of the mechanism controlled thereby, the governors thereafter` being automatically` eiective to substantially. maintain the proper pressure ratios between the low and high pressure sides of the system, the fluid returned to the low .pressure reservoir from the fluid motor serves through conduit 80, valve 11 and conduit 8| being recirculated through the compressor and into the high pressure reservoir.

With reference to Fig. 2 of the drawings, another embodiment of the invention is illustrated, wherein the control valve mechanism actuated by the governors 31 and 68 is somewhat simplified, this embodiment including in general, a high pressure reservoir 6, a low pressure reservoir 1, a compressor 8 which may be of any suitable construction, the compressor being provided with an inlet port or conduit I3 and a discharge port or conduit I 4.A The inlet port I3 is provided with a connection toatmosphere which includes a passage I5 and an atmospheric port I6, communication between the inlet ports and the paslower face of the valve.

A 2,386,046 sage I being'normally prevented lby means of a check valve I1 normally 'maintained in engagement with the valve seat I8 formed at the lower end of the passage |5, through the medium of a spring I3 interposed between the casing and the The discharge port I4 is connected with the high pressure reservoir through the medium of an outlet chamber and a conduit 2| interconnected between the chamber and the high pressure reservoir, a check valve 22 normally maintained in engagement with a valve seat 23 formed at the upper end of the discharge port I4, by means of a spring 24 inter posed between the upper face of the valve and a portion of the casing,` serving to permit passage of the beam 50 to permit the spring 35 to move the valve 32 downward to fully closed position. The fluid motor |04 is provided with a fluid pressure chamber III below the piston, this' chamber being connected with the conduit 4I leading to the high pressure governor ,31, and it will be of uid from the compressorl to the high pressure reservoir and to prevent the passage of uid in the other direction from the reservoir to the discharge port of the compressor. A second outlet chamber 25 is provided as shown, this chamber being provided at its upper end' with a port 26 and at its lower end with a port 21, the port 21 being connected with ,the discharge port I4 through the medium of a passage 28 formed in the casing. The second outlet chamber 25 is connected with the low pressure reservoir 1A through the medium of the conduit 29 while the port 26 at the upper end of the outlet chamber 25 is connected with the inlet portl of the compressor through the medium of a passage 30 and a passage 3| formed in the casing and connected thereto. A valve 32 operable in the same manner as the similarly numbered valve in Fig. 1, serves to control the ilow of iiuid pressure through the ports 2B and 21, the 4valve being normally maintained in the position shown by means of a spring 35 mounted as heretofore described, the stem 33 of the valve having an operative connection with the beam 50 through the medium of a pivot pin 53. The operation of the governors 31 and 68 isidentical with that previo'usly described in connection with Fig. 1, the governor 31 serving on an increase of pressure in the reservoir 6 above a predetermined value to establish a connection between conduits 40 and 4|, and the governor 68 serving on asimilar increase in pressure in the reservoir 1 to establish a connection between conduits 60 and 10.

`The beam 50 is mounted for actuation in a manner slightly different from that illustrated in Fig. 1, however, the right end of the beam being connected with a bracket |00, rigidly mounted with respect to the compressor 8 in any suitable manner, by a link |0I interconnected therebetween, the link being pivotally connected with the bracket |00 by means of a pivotpin |02 and to the right end of the beam 50 by means of a pivot pin |03. The left end of the beam 50 is adapted for actuation in either direction by a pair of iluid motors |04 and |05. these motors likewise being rigidly mounted with respect to the compressor as by means of a suitable bracket |06. The lower motor isprovided with a cylinder |01 having a piston |08 slidably mounted therein, this piston being provided with an upwardly extending piston rod |09 adapted on upward movement to engage the lower face of the beam 50, the piston normally being maintained in the downward position shown throughthe medium of a spring |||J inter ed between the upper end of the cylinder and the upper face of the piston, it being understood that with the piston in the position shown, there is suiiicient clearance between the upper end of the rod |09 and the lower face v stem 33 and the valve 32 to establish a connection pin |03 in an amount sumcient to move the valve stem`33 and the valve 32 upward to a point where the valve serves to close the port 26.

In order that the valve 32 may be moved to mid-position' to unload the compressor, in the manner previously described in connection with the mechanism shown in Fig. 1, the upper uid motor |05 is provided with a cylinder I I2 having a considerably larger bore than the cylinder |01, together with a suitable piston I3 slidably mounted therein and provided with a downwardly extending piston rod 4 adapted on downward to engage the upper face of the' beam 50 and to move the latter downward. The piston I|v3 is normally maintained in upward position by means of a spring H5 interposed between the lower end of the cylinder and the lower face of the piston, and the downward movement of the piston is limited to substantially half that of the piston in the fluid motor |04 `by means of a stop IIE formed on the lower face of the piston and adapted on downward movement thereof to engage the end of the cylinder. I'he upper end of the fluid motor is provided with a fluid pressure chamber I I1 having a connection with the conduit 10 leading to the low pressure governor 68, and the area of the piston with respect to the piston of the lower motor is so proportioned that on the application of pressure to the chamber |I'| on operation of the governor 68 to supply fluid pressure to the motor, the force exerted by the piston I 3 in the downward direction is s ufcient to overcomethe upward force exerted by the piston |08 of the motor |04, the result being that, due to the restricted stroke of the fluid motor |05, the beam 50 is moved downward suiciently to cause the valve 32 to move to mid-position so that the outlet port I4 of the compressor is connected with the inlet port I3 through the passage 28, port 21,

'outlet chamber 25, port 26, passage 30 and pasdrawn into the inlet port I5 past the check valve I1,

the check valve 2 2, the outlet chamber 20 and the conduit 2l, it being understood that when the pressure in the reservoir 6 reaches a predetermined value, the governor 31 becomes operative between conduits 40 and 4I to supply fluid pressure to the fluid motor |04 through the conduit 4I, thus forcing the piston |08 upward and moving the beam 50, the valve upward to their fullest extent in order to effect closure of the port 26 in the outlet chamber 25, thus permitting uid drawn linto the intake of the compressor from atmosphere to be pumped and after compression, supplied to the high lpressure reservoir through the discharge port I4,

into the low pressure whereupon the valve 32 will be in ing uid pressure to said reservoirs,

reservoir 1 through the outlet passage Il, passage 20, port 21, outlet chamber 20 and conduit 2 9. When the pressure in the reservoir 1 reaches a predetermined value, the governor 68 will become effective to establish a connection between conduits 60 and 10, thus supplying fluid pressure through the conduit to the chamber ||1 of the iiuid motor |05, the resulting pressure on the enlarged area of the piston ||3 being sulcient to overcome the upward force exerted by the piston |08 and to force the beam 50 downward until the stop H6 engages the lower end of the cylinder,

and the discharge port of the compressor will be connected with the inlet port through passage 28, port 21, outlet chamber 25, port 26, passage 30 and passage 3 I, and the compressor will be in the for controlling the operation of said compressor for supplying fluid pressure to one or the other or said reservoirs. means controlled by the pressure in the low pressure reservoir'ior controlling the operation of said first named means for preventing the compressor from supplying uid pressure to either of said reservoirs, and means mld-position I unloaded condition. During this cycle of operation, it is understood that fluidv pressure will be supplied to both of the motors |04 and |05, operation of the governor 31 to dis-establish the connection between conduits 40 and 4| and to establish a connection between the conduit 4| and atmosphere serving to .disestablish the connection between conduits 40 and 4| and to connect the latter with atmosphere, thus exhausting fluid pressure from the motor `|04 and permitting the spring 35 to return the valve 32 to the position shown, whileoperation of the governor 68 to disestablish the connection between conduits 60 and 10- and to establish a connection between the conduit 10 and atmosphere while fluid pressure is being supplied to the motor |04 by the governor 31, will serve to deenergize the motor |05 and permit the piston of the motor |04 to move the beam 50 upward to move the valve 32 to its extreme upward position. Thus the control exerted on the operation of the valve 32 by the governors 31 and 68 is substantially similar to that obtained in the mechanism shown in Fig. 1, but a somewhat simplified construction is obtained through the elimination of the relay valve mechanism 38.

There have thus been provided in the two embodiments of the invention illustrated and described, a control mechanism for a compressor of the single-stage type, so constituted as to automatically maintain one pressure in a high pressure reservoir and a lower pressure in another reservoir, together with means for supercharging the compressor with iiuid from the low pressure reservoir in order to permit charging of the high pressurenreservoir by means of a single-stage compressor without utilizing a compression ratio high enough to result in excessive heating conditions such as are ordinarily encountered under conditions of this kind, thus making it possible to i maintain a much higher pressure diierence between the high and low pressure sides of the system with a single-stage compressor than would be possible in systems of the type heretofore utilized. Y

While the two illustrated embodiments of the invention have been shown and described with considerable particularity, it is to be understood that the invention is not limited thereto, but may beembodied in a variety of expressions as will be understood by those skilled in the art. Reference will, therefore, be had to the appended claims for a deilnition of the limits of the invention.

what is claimed is: l

l. The combination in a uid pressure supply system having a high pressure reservoir, a low pressure reservoir and a compressor for supplyoi means controlled by the pressure in said high pressure reservoir for controlling the operation of said rst named means for permitting the compressor to supply iiuid pressure to the low or high pressure reservoir dependent on th degree oi pressure in the latter reservoir.

2. The-combination in a fluid pressure supply system having a high pressure reservoir, a low pressure reservoir and a compressor for supplying iiuid pressure to -said reservoirs, of means for controlling the operation of said compressor for directing the iluid pressure supply therefrom to one or the other of said reservoirs, means controlled by variations of pressure in said high pressure reservoir for rendering said rst named control means effective to direct the supply of fluid pressure to said low pressure reservoir, and means controlled by variations of pressure in said low pressure reservoir for rendering said iirst named control means effective for preventing the flow of pressure to either oi said reservoirs. n

3. The combination in a iluid pressure supply system having a high pressure reservoir, a low pressure reservoir, and a. compressor having an inlet port and 'a discharge port, of means for connecting said discharge port with the high pressure reservoir, means for connecting said discharge port with the low pressure reservoir,

means for connecting said inlet and discharge ports, and means controlled by variations o! pressure in both of said reservoirs for controlling the operation of said connecting means whereby the pressure in both of .said reservoirs is normally maintained at a pressure Yhigher than atmospheric pressure and the pressure in said high pressure reservoir is maintained at a pressure higher than that in the low pressure reservoir.

4. The combination in a fluid pressure supply system having a pair of reservoirs and a compressor having an inlet portand a discharge port, of means for connecting the discharge port selectively with either of said reservoirs for supplying iluid pressure thereto, means for connecting the discharge and inlet ports for preventing said .compressor from supplying iluid 'pressure to either of said reservoirs, and means controlled by variations in pressure in both of said reservoirs for controlling the operation of said con-- necting means.

5. The combination in a iluid pressure supply system having a pair of reservoirs and a compressor having inlet and discharge ports, of means for normally connecting said discharge port with one of said reservoirs for supplying fluid pressureA thereto from the compressor,

means for preventing the flow of fluid pressure from said one reservoir to said discharge port, means for connecting said inlet port with the other reservoir for receiving iiuid pressure therefrom, means for connecting the discharge port with said other reservoir for supplying. uid pressure thereto, and means controlled by variations of pressure in said one reservoir for controlling the operation oi said connecting means.

6. The combination in a iluid pressure supply system having-a pair of reservoirs and a compressor for supplying fluid pressure thereto having inlet and discharge ports, of means including a control valve operable for selectively connecting said discharge port with one oi' said reservoirs or with said inlet port, means for connecting said discharge port with said other reservoir, and means controlled .by variations of pressure in both of said reservoirs for controlling the operation of said first named control'means.

7. The combination in a iiuid pressure supply system having a pair of reservoirs and a compressor provided with inlet and discharge ports for supplying iiuid pressure to said reservoirs, of means including a valve for controlling the iiow of fluid pressure between said ports and between said ports and reservoirs for rendering the compressor effective to supply uid pressure to either of said reservoirs and for rendering said compressor ineffective to supply iiuid pressure' and operable when the pressure therein exceeds a 'predetermined value for controlling the operation to either of said reservoirs, and means respon- Y sive to variations in pressure in both of said reservoirs for controlling the operation of said means.

8. The combination in a iiuid pressure supply system having a pair of iluid pressure reservoirs and a compressor-for supplying fluid pressure thereto having inlet and discharge ports having a connection therebetween and connections with said reservoirs, of means for controlling the connection between said ports and for controlling the connections between said ports and reservoirs for selectively establishing a connection between'the discharge port and the low pressure reservoir, between the low pressure reservoir and the inlet port and between the discharge port and the -inlet port, and means responsive to variations of pressure in said reservoirs for controllingthe operation of said connection controlling means.

9. The combination-in a uid pressure supply system having a pair of reservoirs and a compressor for supplying uid pressure thereto, said compressor being provided with inlet and discharge ports, of means for connecting saidV discharge port with one of said reservoirs, means including a valve operable in one position for establishing a connection between said other reservoir and said inlet port, operable in another position for establishing a connection between said discharge port and inlet port and operable in the third position for establishing a connection between said inlet port and said other reservoir, and means controlled in response to variations of pressure in both of said reservoirs for controlling the operation of said valve'to establish said connections, whereby the pressure in said one reservoir is maintained at a pressure higher than that in said other reservoir and the pressure in said other reservoir is maintained at a pressure above atmospheric pressure.

l0. The combination in a fluid pressure supply system having a high pressure reservoir, a low pressure reservoir and a compressor provided with an inlet port and a discharge port for supplying iluid pressure to said reservoirs,of means for connecting said discharge port with said high pressure reservoir, means for preventing the flow of uid pressure through said connecting means from said high pressure reservoir to said discharge port, means responsive to variations of pressure in said high pressure reservoir and operable when the pressure therein exceeds a predetermined value for establishing a connection between said discharge port and low pressure reservoir, means controlled by variations in pressure in said low pressure reservoir of said connection establishing meansIk to establish communication between the low` pressure reservoir and the inlet -port of 4the compressor whereby the fluid pressure in the low pressure reservoir is recompressed by the compressor and i i means for connecting said discharge port with p either of the reservoirs for supplying iiuid pressure thereto and for connecting the inlet port with one of the reservoirs for receiving fluid pressure therefrom, and means controlled by variations of pressure inthe other of said reservoirs for controlling the operation of said connecting means. y i

12. The combination in a uid pressure supply system having a pair of reservoirs and a compressor having inlet and discharge ports, of means for connecting the discharge port with one of the reservoirs, means including a valve operable in one position for connecting said other reservoir and inlet port, in another position for connecting said inlet and discharge ports, and in a third position for preventing communication between said other reservoir and inlet port, and means for controlling the operation of said valve and for moving the latter to said positions including a iiuid actuator responsive to variations of pressure in said one reservoir and a second uid actuator responsive to variations of pressure in said other reservoir.

13. The combination in a uid pressure supplyl system having a pair of reservoirs and a cornpressor having inlet and discharge ports, of means for connecting the discharge port with one of the reservoirs, means including a valve operable in one position for connecting said other reservoir and inlet port, ina second position for connecting said inlet and discharge ports, and in a third position for preventing communicationbetween said other reservoir and inlet port, means for normally maintaining said valve in the irst named position, means including a pair of fluid actuators controlled by the pressure in said one reservoir for moving the valve to said third position, and'means controlled by the pressure in the other reservoir for deenergizing one of said actuators and permitting movement of the valve to said second position under the action of said maintaining means.

' in a third position for. preventing Vcommunication between said other reservoir and inlet port,

means for normally maintaining said valve in the iirst named position, means including a uid .actuator responsive to the pressure in said one position for connecting said inlet and dis-v charge ports-and in a third position for preventing communication between said other reservoir and inlet port, means for normally maintaining said valve in the rst named position, a fluid actuator for moving the valve to the third position, a second uid actuator for moving the valve from the third to the second position, means controlled by variations of pressure in said one reservoir for supplying uid pressure to the first named actuator when the pressure 'in said one reservoir exceeds a predetermined value, and means .controlled by variations of pressure in said other reservoir for supplying iluid pressure to said second actuator when thev pressure in said other'reservoir exceeds a predetermined value.

16. The combination in a iluid pressure supply system having a pair of reservoirs and a compressor having inlet and discharge ports, of means for connecting the discharge port with one of the reservoirs',l means including a valve operable in one position for connecting said other reservoir and inlet port, in a second position for connecting saidV inlet and discharge ports, and in a third position for preventing communication between said other reservoir and inlet port, means for normally' maintaining said valve in the first named position, a pair of fluid actuators for moving the valve to said third position, valvular means con trolled by variations of pressure in said one reservoir for supplying fluid pressure to said actuatorsto move the valve to said third position when the pressurein said one reservoir exceeds movement of said valve to said second position by said maintaining means.

17. The combination in a iiuid pressure supply system having a pair of reservoirs and a compressor having inlet and discharge ports, of means for connecting the discharge port with one of the reservoirs, means including a valve operable in one position for connecting said other reservoir and inlet port, in a second position for connecting said inlet and discharge ports. and in a third position for preventing communication between said other reservoir and inlet port, means for normally maintaining said valve in the rst named position, a pair of tluid actuators for moving the valve to said third position, valvular means controlled by variations of pressure in said one reservoir for supplying uid pressure to said actuators to move the valve to said third position when the pressure in saidone reservoir exceeds a predetermined value, a iluid pressure operated valve` for controlling the supplying of fluid pressure to one of said actuators by the operation of said valvular means, and means controlled by variations of pressure in said other reservoir for supplying iiuld pressure for operat` ing said control valve when the pressure in said other reservoir exceeds a predetermined value.

18. The combination in a duid pressure supply system having a pair of reservoirs, a compressor for supplying uid pressure thereto and connections between the compressor and both of said reservoirs, of control means for controlling said connections for permitting the supplying oi' a dierent predetermined pressure to each of said reservoirs and for preventing the supplying `oi fluid pressure to either reservoir when said prea predeterminedv value, and means controlled by i' variations of pressure in said other reservoir for preventing the supplying of fluid pressure to one l of said actuators by the operation of said valvular determined pressures are established, and means controlled by variations of pressure in both reservoirs for controlling the operation of said control means. i

19. The combination in a iluid pressure supply system having high and low pressure reservoirs and a iluid pump, of means for selectively connecting the pump to pump iluid -to the high pressure reservoir, to pump iluid to the low pressure rservoir, to pump fluid from the low pressure reservoir to the high pressure reservoir, and to prevent the pumping of iluid to either of the reservoirs, and means controlled by variations of pressurein said reservoirs for controlling the operation of said connecting means.

, ELBERT FOWLER. 

